Which of the following A-Train satellites is NOT currently active?

The choice identifying PARSOL as the satellite that is not currently active is based on its operational history. PARSOL (the Polarization and Anisotropy of Reflectances for Atmospheric Sciences) was a part of the A-Train satellite constellation focused on remote sensing of the Earth's atmosphere and surface. However, PARSOL was decommissioned and is no longer operational.

In contrast, Aqua, CALIPSO, and Aura are active satellites within the A-Train that continue to contribute valuable scientific data. Aqua, launched in 2002, studies Earth's water cycle. CALIPSO, launched in 2006, focuses on the characterization of clouds and aerosols in the atmosphere. Aura, launched in 2004, observes atmospheric composition and is important for studying air quality and climate change. These satellites play integral roles in ongoing Earth observation missions, maintaining their relevance in climate and atmospheric research.